The Universe, Solar System, and Planets I · The Universe, Solar System, and Planets I Questions: How do we know the Big Bang happened? How do we know the Universe is expanding? What

The Universe, Solar System,

and Planets I

Questions:

How do we know the Big Bang happened?

How do we know the Universe is expanding?

What is the timeframe of Universe evolution?

News Flash: NASA/CNN report first starsformed early than once thought

Edwin Hubble at Mt. Wilson

Hubble guiding the Hooker

100 inch telescope in 1923.The Hooker 100 inch telescope atop Mt. Wilson

near Pasadena, CA. It was the largest telescope in

the world from 1917-1947.

Hubble’s observations at the 100 inch during the1920’s led him to the conclusion that the universe is expanding, and that an object’s recession velocityis proportional to its distance from the observer.

A deep image of an “empty”portion of the sky with the

Hubble Space Telescope

reveals that the universe is

filled with galaxies- many just

like our own. The light

we see from the most distant

galaxies has traveled approx-

imately 10 billion years to

reach us.

Deep Hubble Space Telescope Image

Using the Doppler Effect to Measure Velocity

Blueshift Redshift

Calcium

Magnesium

Sodium

Galaxy Spectrum

Stellar Spectrum

Spectra of a nearby star and a distant

galaxy

Star is nearby, approximately at rest

Galaxy is distant, traveling away from

us at 12,000 km/s

Galaxy Spectroscopy

Origin of the Universe -

Did It Begin with a Big Bang?

Penzias and Wilson, 1965 Arecibo Dish, Puerto Rico

Discovery of the Background Radiation from initial Big Bang

-Long wavelength

-came from all directions

Early History of the Universe

• Matter as we know it did not exist at the time of the Big Bang, only pure

energy. Within one second, the 4 fundamental forces were separated

– gravity - the attraction of one body toward another

– electromagnetic force - binds atoms into molecules, can be

transmitted by photons

– strong nuclear force - binds protons and neutrons together in the

nucleus

– weak nuclear force - breaks down an atom’s nucleus, producing radioactive decay

Early History of the Universe

• After 3 minutes, photons and neutrons began

to fuse to form the nuclei of hydrogen and

helium atoms

• About 300,000 years later, temperatures were

cool enough for complete hydrogen and

helium atoms to form

• Photons escaped from matter about the same

time, and light existed for the first time

Changing Composition of the

Universe

• 200 million years later, with expansion still occurring, stars and galaxies

began forming from leftover matter - hydrogen and helium

– nuclear fusion in stars has reduced the original composition of 100%

H and He to 98%

– when a dying star explodes, the heavier elements created by fusion

are blown into space to be recycled by newly forming stars

– the overall composition of the galaxies is gradually changing to the

heavier elements

The Solar System - Its Origin and Early Development

Our solar system, part of the Milky Way galaxy, consists of the Sun, nine planets, 64 known moons, many asteroids, millions of comets and meteorites, as well as interplanetary dust and gases

The Solar System - Its Origin and Early Development

General Characteristics of the

Solar System

• Planetary orbits and rotation

– planet and satellite orbits are in a common plane

– nearly all planet and satellite orbital and spin motions are in the same direction

– rotation axes of nearly all planets and satellites are roughly perpendicular to the plane of the ecliptic

General Characteristics of the

Solar System• Chemical and physical properties of the planets

– the terrestrial planets are small, have a high density, and are composed

of rock and metallic elements

– the Jovian planets are large, have a low density, and are composed of

gases and frozen compounds

• Slow rotation of the Sun

• Interplanetary material

– existence and location of asteroid

belt

– distribution of interplanetary dust

Meteorites -

Visitors from Outer Space

– Stones - composed of iron and magnesium silicates,

about 93% of all meteorites

– Irons - composed of iron and nickel alloys

– Stony-Irons - nearly equal amounts of iron and nickel

and silicate minerals

• Meteorites are believed to be pieces

of material that originated in the

formation of the Solar System about

4.6 billion years ago

• Size and Scale of the Universe

Size and Scale of the Universe

Image courtesy of The Cosmic Perspective by Bennett, Donahue, Schneider, & Voit; Addison Wesley, 2002


• Planet where we

all live

• Comprised

primarily of rock

• Spherical in shape

• 12,700 km in

diameter

• It would take 17

days to

circumnavigate the

globe driving a car

at 100 km/hr (62

mph)Image Credit: NASA/JPL/GSFC

19

20

EARTH

Mercury

Venus

Mars

21

22

Earth

Saturn

UranusNeptune

Jupiter

Pluto (not a planet) and its moon Charon

23

The Sun

is our nearest star

24

The Solar System

25

The Milky Way(Our Galaxy)

A hundred, thousand, million stars!

26

the Milky Way as seen from the Enterprise

A hundred thousand light years across

Light would take 100 000 years to travel across the galaxy.

27

Distances

• It takes 8 minutes for light to reach us from the Sun.

• A light-year is the distance travelled by light in 1 year.

• The Sun is our nearest star.

• Our next nearest star, Alpha Centauri is 4 light years away.

• The Milky Way is 100 000 light years across.

28

The local group of galaxies

Andromeda is the nearest biggalaxy to theMilky Way

Milky Way

29

Light from Andromeda takes

2 million years to reach us.

Milky Way

Andromeda

30

Local group

The Local Supercluster

Here the local group has shrunk to the size of the Milky Way in the last slide.

31

It left when the dinosaurs were on Earth.

Light from Virgo has taken 65 million years to

reach us.

Virgo Cluster

32

The Universe is mind-bogglingly big!

• The Sun is about 150 000 000 km away from

Earth

• Bright stars in the night sky are about 1000 000 (1

million) times as far away as the Sun.

• The near galaxies are about 100 000 times as far

away as the bright stars.

– 15 000 000 000 000 000 000 km

33 NASA


• The star that Earth

orbits

• Composed primarily of

hydrogen and helium

gas

• Uses nuclear fusion in

its core to generate heat

and light to allow itself

to resist the crushing

weight of its own mass

• Spherical in shape

• 1.39 Million km in

diameter

Image Credit: SOHO/NASA/ESA


• The Sun’s diameter is 109 times greater than

that of Earth

• Over 1 million Earths

would fit inside the

Sun’s volume

• The average distance

between the Earth

and the Sun is called

an Astronomical Unit

(AU) - it is about150

million kilometers

• It would take 11,780

Earths lined up side to

side to bridge the gap

between Earth and Sun

(or 107 Suns)Image Credit: SOHO/NASA/ESA


• 8 planets, several dwarf

planets, thousands of

asteroids, and trillions of

comets and meteoroids

• Mostly distributed in a flat

disk

• Pluto orbits ~40 AU from Sun• The Sun blows a constant

wind of charged gas into

interstellar space, called the

Solar Wind

• The boundary between the

Solar Wind and interstellar

space (the Heliosphere) is

Imag

e credit: N

AS

A

Imag

e cr

edit

: N

AS

A/J

PL

-Cal

tech

/R. H

urt

Imag

e credit: N

AS

A


• The region of the

Galaxy within about

20 light-years of the

Sun (40 light-years

diameter)

• A light-year is the

distance that light

travels in one year

(~10 trillion

kilometers or 63,000

AU)

• The neighborhood

stars generally move

with the Sun in its Image credit: Andrew Colvin


• The Milky Way Galaxy

is a giant disk of stars

100,000 light-years

across and 1,000 light-

years thick

• The Sun is located at the

edge of a spiral arm,

30,000 light-years from

the center

• It takes about 250

million years for the Sun

to complete one orbit

• There are over 200

billion stars in the Milky

Way

Image credit: R. Hurt (SSC), JPL-Caltech, NASA


• About 6.5 million

light-years in

diameter

• Contains 3 large

spiral galaxies --

Milky Way,

Andromeda(M31)

, and

Triangulum(M33)

-- plus a few

dozen dwarf

galaxies with

elliptical or

irregular shapes

• Gravitationally Image Credit: Andrew Colvin


• The Local

Supercluster is about

130 million light-

years across

• It’s a huge cluster of thousands upon

thousands of galaxies

• Largest cluster is the

Virgo cluster

containing well over

a thousand galaxies

• Clusters and groups

of galaxies are

gravitationally bound

together, however the

Image credit: Andrew Colvin


• Great walls and filaments

of galaxy clusters

surrounding voids

containing no galaxies

• Probably at least 100

billion galaxies in the

Universe

• Surveys of galaxies reveal

a web-like or honeycomb

structure to the Universe

Image Credit: Dr Chris Fluke, Centre for Astrophysics and Supercomputing,

Swinburne University of Technology

Image Credit: G.L. Bryan, M. L. Norman, UIUC, NCSA, GC3

• Computer simulations also show a

similar structure, often called the

“Cosmic Web”


Image Credit: Springer et al (2004)

• The Observable Universe is

currently about 91

billion light-years across

• There could be (and

likely is) much more

beyond that, but we

cannot see it from this

point in spacetime

• Note: The matter that

we can see glowing

shortly after the Big

Bang (detected by the

light it emitted 13.7

billion years ago) is

Most people have seen the curved Space-

Time figure, so let’s understand those!

The size of the Sun… Remember:Diagram shows the CURVATURE of Space-time

Draw the dent to be deepest is where the force is largest Where space is falling to the center “fastest”

Nothing to “See”43

44

How the Curvature Changes as we

Compress the SunWhat if we compressed the Sun

into a Neutron Star? Far outside the Sun

you can’t really tell the difference

• Force is the same

You can tell the

difference if you are

very close to the Sun

itself

• Force is bigger

The sun is now a few kilometers across

45

Compress the Sun into a Black Hole

Infinite curvature

Curvature is VERY different really close to where the mass

isNothing “curved” to SEE, deeper

just means where space

falling in fastest

Remember: The black hole is just a point in space

46

The Sun in Space-TimeThe size of the Sun…

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The Universe, Solar System, and Planets I · The Universe, Solar System, and Planets I Questions: How do we know the Big Bang happened? How do we know the Universe is expanding? What